Flight 2

Attempt 1

Attempt 1 did not result in engine ignition. The Launch Control Officer reported that the igniter had continuity, but it either shorted or was manufactured improperly. Igniter was retained and investigated. The most likely cause of failure to the igniter was physical damage to the pyrotechnic material of the igniter sustained when the igniter plug was pushed into the motor. It appears as if the plug pushed the two wires just far enough apart that they were unable to get hot enough to cause the pyrotechnic material to ignite. This is a known failure mode of this type of igniter, and is a large part of why the Estes motor kits include six igniters for three motors.

Attempt 2

A new igniter was inserted into the motor for attempt 2. Flight 2 lifted off from pad B1 at 2023-04-08 13:55 on an Estes C6-5 and flew without incident. Ejection charge fired near apogee. Descent was controlled and appeared to be smooth from the ground. The motor was retained and all wadding was cleanly ejected. Parachute and elastic cord were intact and not singed. The rocket was dragged across the ground for a short distance after landing.

Upon inspection, a dent approximately 4 cm wide (perpendicular to long axis) and 1.5 cm tall indentation was found to the forward end of the main body tube. At its greatest extent, the tube had been deflected approximately 0.5 cm towards the midline. No damage was noted to the nose cone, indicating that the dent could not have been sustained prior to the firing of the ejection charge.

There was some chipping to the layer of primer on the outside of the body tube. No significant structural damage was found and the body tube was easily hand-manipulated back into a state where immediate reflight would be possible.

Video

Video was recorded on a Sony Xperia 5 III (2160x3840 @ 23.97 fps, progressive scan) and brought into Sony Vegas 16 for frame-by-frame analysis.

All times are in seconds relative to liftoff. Owing to the framerate of the video, all events (except liftoff) include a +/- 41.7 ms uncertainty.

T+ (sec)	Description
0.000	Liftoff - the last frame in which the rocket shows no motion relative to the pad.
0.042	Rocket is in motion and a smoke plume is clearly visible.
0.125	The rocket has cleared the launch rail.
0.135	Sound from the rocket reaches the camera. Using 340 m/s (761 mph) for the speed of sound, this translates to a distance of 46 m (~151 ft) between the rocket and camera, which seems reasonable. Exact positions of the camera and launch pad were not recorded and cannot be reconstructed.
1.920	Motor burnout. This is defined as the first frame in which the smoke output from the motor noticeably decreases, as seen in the photos below.
5.675	The ejection charge begins to fire, as evidenced by a puff of smoke appearing at the rocket and trailing out the back.
6.301	Smoke trail from ejection charge stops.
6.802	Main ejection charge fires. A large puff of smoke is seen near the rocket.
7.011	Wadding can be seen falling free from the rocket.
7.512	Chute can be seen.
42.649	Contact with ground.

Analysis

Major events:

	Simulated (sec) *	Actual (sec)	|Difference| (sec)
Ignition	0.000	0.000	0.000
Burnout	1.874	1.920	0.046
Apogee	6.440	unknown **	N/A **
Chute Deploy	6.875	6.802	0.073
Motor Burnout-to-Deploy Delay	5.001	4.882	0.119
Landing	42.066	42.649	0.583

Flight phases:

Flight Phase	Duration (sec)
Powered Ascent	1.920
Ballistic Travel (ascent and descent)	5.580
Descent under Chute	35.137
Total	42.649

Motor Performance

The motor burn time as measured from video is 1.920 seconds (+/- 41.7 ms), which is remarkably consistent with the 1.9 s measured burn time listed on thrustcurve.org, and 46 ms off from OpenRocket’s simulated burn time of 1.874 seconds.

There was only a 0.119 second difference between the expected 5 second deploy charge delay and the measured 4.882 second delay. The NAR lists an average measured delay of 4.28 s for this motor, though that report was last updated in August of 1996, and it is likely that Estes has improved on their delay time since then.

Apogee and Deployment

The OpenRocket simulation estimates an apogee of 197 m (~646 ft), and based on how well other aspects of the simulation match the actual flight, this estimate seems reasonable.

After the chute deployed, the craft appeared on video to be flipping end-over-end. This motion was not observed from the ground, though this is likely due to the difficulty involved in making out details at that distance.

Assuming an apogee of 197 m and taking the measured descent time of 35.847 sec, the average descent rate was 5.5 m/s. This differs significantly from the projected touchdown speed of 4.56 m/s. It is possible that the chute had not fully opened while the rocket was flipping end-over-end, and that this produced two distinct modes of descent; one where the rocket is in near-freefall due to a partially opened parachute, and one where the rocket is descending under a fully-opened chute. An alternate explanation is that the aerodynamics of descent under a parachute with a spill hole is different enough from a descent under a continuous parachute to be noticeable even under such a relatively short descent.

Landing and Recovery

The rocket first contacted the ground on two fins with the forward end of the body tube oriented towards the camera. The craft was then pulled downwind, away from the camera, with the two fins in contact with the ground acting as a fulcrum. From here, the rocket rotated until the body tube made contact with the ground, and the whole craft was dragged a short distance by the wind acting on the parachute.

It is interesting to note that although it seems likely that the dent on the forward end of the body tube would have come from this rotation into the ground about the two fins, the side of the body tube that made contact with the ground was the side directly opposite the dent. In fact, the dent was found on the side of the rocket facing up once the craft had come to a rest. This leaves the most likely cause of the dent to be contact between the body tube and nose cone during the end-over-end tumbling that the rocket experienced after parachute deployment. This notion is further bolstered by the fact that no dirt or dust was found on or near the dent.

After landing, wind dragged the craft across the ground by the parachute. Video quality was not high enough to accurately estimate how far the rocket was dragged, but the distance was not far (in the ballpark of 1 to 2 times the length of the body tube) and no significant damage was done to the craft.